Recent studies have shown that a significant portion of older people have an elevation of intraocular pressure. In a certain percentage of these patients the elevated intraocular pressure represents an early stage of glaucoma. In the other patients the pressure is a benign process that will not cause any damage to their eyes. At present it is not possible to differentiate between these two groups of patients. This is unfortunate because ideally one would like to begin treatment of the patients with glaucoma as soon as possible but avoid exposing the "normal" patients to the risks of drug therapy. The present project is designed to develop and test a method that may permit the identification of these two groups. We believe that individuals susceptible to glaucomatous damage are those with a relatively weak mechanical support at the optic nervehead. We therefore propose the development of a noninvasive method, that uses laser doppler velocimetry, to measure optic nervehead rigidity, in vivo. Preliminary results obtained in postmortem human eyes show that the method is feasible. An instrument suitable for the study of intact human eyes will be constructed and then tested in animals to ascertain the safety and reliability of the method. Once this phase of the study has been completed, intact normal and glaucomatous eyes will be studied to determine if the postulated differences are indeed present and thus to assess the specificity of the test. Its sensitivity, i.e., its predictive value, may be the subject of a clinical study following the completion of the present research.